This invention relates generally to the provision of compositions for the topical application of a water soluble active ingredient to a surface of a warm blooded animal including humans. In particular, this invention relates to such a composition which can be applied as a relatively low viscosity flowable liquid and which will quickly, upon contact with the warm surface of such animal, turn into a relatively high viscosity, essentially non-flowable, gel.
The field of applying active ingredients topically to humans and animals is, of course, wide ranging and comprises for example, the application of active ingredient for therapeutic, prophylactic and cosmetic purposes. Notwithstanding this wide and varying range of purposes, a great many of such applications suffer from a common problem. Specifically, it is desirable to provide such compositions in a pourable, flowable liquid form so that containers for the composition can easily be filled, the composition can easily be dispensed from such containers and the composition can easily be applied to the desired situs; either by mechanical means e.g., a syringe and needle, a spray or pump, or by hand. On the other hand, once the composition has been packaged, dispensed and applied to the situs, it is desirable that the composition no longer flow but instead remain in place and release the active ingredient.
As an example, it is desirable to topically apply certain therapeutic liquids into subgingival pockets in the treatment of periodontal disease. Injection devices employed for the purpose utilize fitments with small orifices to enable the injection tip to fit into the subgingival pocket easily without inflicting excessive pain to a patient. An example of such a device is described in U.S. Pat. No. 4,617,918. Clearly, to flow through the small orifices of such devices, the composition must be of relatively low viscosity and easily flowable. Once delivered to the subgingival pockets, however, it is desirable that the composition remain in place and deliver the medicament to the affected tissue. A low viscosity fluid will obviously not suffice for this purpose.
The problem of providing a composition having these apparently contradictory properties (i.e., flowable during filling, dispensing and applying while non-flowable after being applied to the desired situs) has been addressed in U.S. Pat. No. 4,411,889 to Caslavsky, et al. This specification teaches the provision of a composition for topical delivery of fluoride or antibacterial agents to the oral cavity and employs a composition said to be a low-viscosity, aqueous solution adapted to be converted, after mixing and topical application, from a liquid solution to a gel state. The operative ingredients in this invention comprise a silica acid ester monomer or prepolymer which on hydrolysis forms silica polymer when in the presence of one or more gelling agents such as gel catalysts or silicate esters. The gelling is initiated and it is taught that from anywhere from 24 hours to less than one minute after combining the gelling agent with the remainder of the composition, gelling is effected. Thus while the composition accomplishes the result of in situ gelling after application, in practice, several drawbacks are manifested. In use, it is incumbent upon the applier to first mix the composition with the gelling agent and hence requires weighing and/or measuring and mixing; operations which are clearly inconvenient to a professional and totally impractical to a lay consumer. Moreover, there is an exquisite timing requirement in using such compositions: the mixing must occur closely enough to application so as to provide sufficient working time prior to gelling and yet upon application the composition must gel quickly enough to realize the benefits of an applied gel. Such precise timing once again represent great inconvenience for the professional and essentially precludes use by the lay user.
Accordingly, there is a need for a composition which can be filled and stored, as a flowable liquid, dispensed as a liquid and, without the need for any further mixing or measuring, applied to a desired situs where it will quickly form, in situ, into a gel.